avformat/mxfenc: Remove redundant DNXHD frame size checks

The actual frame_size is no longer used since commit
3d38e45eb85c7a2420cb48a9cd45625c28644b2e; and the check for
"< 0" is equivalent to the CID being valid. But this is already
checked by avpriv_dnxhd_get_interlaced() (and is actually already
ensured by mxf_dnxhd_codec_uls containing this CID).

Reviewed-by: Tomas Härdin <tjoppen@acc.umu.se>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavformat/mxfenc.c

@@ -2065,7 +2065,7 @@ static int mxf_parse_dnxhd_frame(AVFormatContext *s, AVStream *st, AVPacket *pkt
 {
     MXFContext *mxf = s->priv_data;
     MXFStreamContext *sc = st->priv_data;
-    int i, cid, frame_size = 0;
+    int i, cid;
 
     if (mxf->header_written)
         return 1;
@@ -2093,12 +2093,6 @@ static int mxf_parse_dnxhd_frame(AVFormatContext *s, AVStream *st, AVPacket *pkt
     if (!sc->component_depth)
         return 0;
 
-    if ((frame_size = avpriv_dnxhd_get_frame_size(cid)) == DNXHD_VARIABLE) {
-        frame_size = avpriv_dnxhd_get_hr_frame_size(cid, st->codecpar->width, st->codecpar->height);
-    }
-    if (frame_size < 0)
-        return 0;
-
     if (cid >= 1270) { // RI raster
         av_reduce(&sc->aspect_ratio.num, &sc->aspect_ratio.den,
                   st->codecpar->width, st->codecpar->height,